I've been battling a lean spike condition resulting in 17-18 afr's sometimes backfiring for the past moth since installing this turbo kit. My maf is in a 3" pipe using a diablo mafia range extender to increase allow the stock maf to correctly read the increased air flow. I have scaled and rescaled my maf trasnfer function several times using 2 different methods and came up with the same x-fer each time so I'm pretty sure its in good shape. Its basicly scaled 1.59x over stock.
I've done alot of searching on this forum and other tuning forums and it seems this is a fairly common issue one newer model modified fords. 2 advised fixes that come up are 1) manifold volume and 2) transient fueling. I have tried both with no success. 1) My manifold volume stock is 10.9 liters. I tried 8 liters which did seem to help lessen the severity of the lean out but induced a lean/rich/lean/rich/lean/normal buck-surge.
2) transient fueling didnt seem to work as i interperetted it would. I played with all the tables sometimes scaling them 1.59x to match the amount my maf had changed or 1.2x. The table i put my hope is was under "acceleration" 'gain at start up'. Increases here did seem to help but as i increased these values my start up got so rich as to the point it would not start or run with afrs showing in the 10's if it did manage to chug itself to life.
Maybe my understanding of how to use the transient tables is misguided, but it seems like we are missing the parameter (accelerator pump shot) i need.
The car has a very slight lean tip in once its at operating temp but only bumps up to 15.5 for at most for a split second before maintaing a mid 14 afr. It is worst with a cold engine and gradually goes away as temps increase. any suggestions?